Generally an epoxy resin composition has excellent electric performance and adhesive strength. Therefore, it has been used in the past for various uses of electric or electronic fields.
In cases where only insufficient results can be obtained even when a conventional epoxy resin is used alone or by mixture, cyanate ester-epoxy composite resin compositions comprised of mixing epoxy resin with cyanate ester are in heavy usage as a resin composition available for sealing of semiconductors or molding wherein high thermal resistance is required.
For example, resin compositions comprised of cyanate ester, epoxy resin and dicyandiamide or the like have already been proposed (Patent document 1). However, they have disadvantages in that a high curing temperature and long curing time are required. Therefore, the resin compositions having satisfactory characteristics have not been obtained yet.